On March 15, 220 AD, Cao Cao died of illness, he was suspicious by nature, and mistakenly killed many virtuous and loyal subjects, which is a typical personality of ning negative people who cannot bear the world. However, he did not hesitate to kill Xun Yu to sweep away his own path to becoming emperor, and finally fell sima Yi, and he was unable to sit on the throne until his death. In 220, Cao Pi declared himself emperor, but six years later Cao Wei was replaced by Sima Yi.
Sima Yi, who was already 70 years old at the time, overthrew Cao Wei in only five days with three thousand elite soldiers, and he said that he could do so quickly, thanks to Cao Pi's help, it turned out that during Cao Pi's reign, he vigorously suppressed the military power of the kings of the various domains, hoping to consolidate his position, resulting in the lack of elite troops in the garrisons, and it was so quickly breached.
In 191 AD, Xun Yu believed that Yuan Shao could not achieve great things, so he came to Cao Cao, thus opening the beginning of Cao Cao's unification of Northern Wei. In 194 AD, Xun Yu suggested that Cao Cao march east to Xuzhou Mu, and the following year Cao Cao garrisoned Juye and besieged Lü Bu's general, Lü Bu personally went to the rescue, only to be defeated by Cao Cao, and in 196 Cao Cao began to greatly promote the Tuntian system, preparing to meet Yuan Shao's army in Hebei, and in 200 AD the two armies launched a campaign at Guandu.
Finally, the situation with Sun Quan and Liu Bei's three kingdoms was determined. However, as Cao Cao became more and more powerful, his disagreements with Xun Yu also grew, because Xun Yu was still bent on supporting the Han Dynasty, and although Xun Yu helped him unify the north, in order not to let him stop himself, Cao Cao finally dismissed him and sent him down, and finally even poisoned him.
However, people like Xun Yu, Cao Cao decisively disposed of, Sima Yi such ambitions written on his face, Cao Cao actually left him to the end, and he also took away the world. Since Cao Cao was the lowest of the Three Kingdoms, Sima Yi resisted accepting the official position given by Cao Cao, but Cao Cao had no advisers under his command and had to get Sima Yi's support, so he forcibly recruited him as a literary rafter, which made Sima Yi begin to support Cao Cao as emperor.
However, Cao Cao also knew that Sima Yi was a dangerous person and that it was not appropriate to stay around for a long time, but he was looking for himself to urgently need someone, so he saved his heart to get rid of him later, who knew that before he could become emperor, he died of illness in 220 AD. After Cao Cao's death, Cao Pi succeeded to the throne, forcing emperor Chan of Han to abdicate and become Emperor Wen of Wei, posthumously honoring Cao Cao as Emperor Wu.
During Cao Pi's reign, he established the Nine Pins Zhongzheng system, examined the candidates for admission with virtue, and also quelled the rebellions of Jiuquan and Zhangye, and took back the three counties of Shangyong. In order to consolidate his throne, he ordered that all the imperial clans of the Cao family be repatriated to their garrisons and not allowed to enter luoyang, the capital of the capital. He also sent an emissary to the garrison to monitor the kings of the clans, returned to the dynasty every year to make a detailed report, and also took back all the military powers of the kings of the clans, in order to prevent them from garrisoning troops, the number of troops in each garrison should not exceed a certain amount, which led to the fact that the princely states around Luoyang had no elite troops to use.
In 249, Sima Yi was already 70 years old, and when Cao Shuang left Luoyang, he led three thousand elite soldiers to break through the surrounding cities all the way, drove straight into Luoyang, took Luoyang in only five days, seized Cao Wei's military power, and Cao Wei's world has since existed in name only. The reason why Sima Yi was able to drive straight in and take Luoyang effortlessly was really thanks to the loopholes that appeared when Cao Pi was too centralized.